MISRII is a member of the TGF-2 family of receptors. MIS receptor expression is embryologically important in the regression of the m|llerian ducts in the male fetus after activation by MIS (ligand) secreted by the testis. This tissue-specific pattern of MISRII expression in gynecologic tissues persists in the adult. We further show this specific pattern of expression persists in the majority of gynecologic cancers supporting its relevance as a specific target of anti-cancer therapy. To that end we have been investigating the general hypothesis that MISRII is a tissue-specific receptor (target) present in gynecologic cancers which, additionally, is fundamentally linked to serine/threonine receptor-mediated pathway(s) resulting in growth inhibition and/or cell death. These concepts suggest two primary and independent therapeutic strategies: 1) utilize ligand to target MISRII directly resulting in decreased proliferation or potentiation of cytotoxic therapy, and/or 2) using the MISRII receptor as a target to specifically deliver therapy or to improve imaging, either of which would be independent of downstream signaling. Despite the appeal of this approach prior investigations have suffered from key limitations: (i) lack of delineation of the relevant T1R and downstream signaling components necessary for MIS activity;(ii) lack of attempt to interpret MIS response with expression of relevant T1Rs;(iii) expression studies based on continuous cancer cell lines fail to reflect the expression pattern in primary cancers;(iv) lack of models to adequately assess rhMIS bioactivity in cancer cell model. This information is vital for rational design and application of any MIS-based strategy: absent this, meaningful interpretation of prior in vitro studies using MIS is impossible. In this revised application we show preliminary data and experiments designed to address these limitations. Based on our work with other TGF-2 family receptors we have designed experiments to determine the role(s) and status of T1R and T2R in MIS signaling (Aim 1). The required receptor complexes regulating Smad signaling and cell growth inhibition can will then be tested in vitro in primary cancer cultures (Aim 2) and allow us to define the specific parameters in which MIS directed therapy may be effective. Finally, we will pursue the alternative therapeutic strategy which is not predicated upon MIS- dependent signaling: using MISRII as a highly specific target to bring other therapeutic agents or imaging molecules to specific gynecologic cancers (Aim 3). Collectively, this application will provide the necessary insight into the biology of MIS signaling in gyncecologic cancers, and provide the essential data for design and interpretation of human trials targeting MISRII. PUBLIC HEALTH RELEVANCE: Relevance to the public health (lay language): Management of advanced ovarian and uterine cancers is inadequate and most patients with advanced disease will die of their cancer. To make progress in the management of these cancers, novel and specific targets that distinguish cancer cells from normal cells are needed. MISRII is a receptor present specifically in the majority of these cancers. This provides a unique target that distinguishes the cancer cells from normal cells. Some evidence suggests that activating this receptor by exposing it to its hormone (MIS) results in growth arrest and increased sensitivity to chemotherapy. While some work has been done in this field it has been limited by: (i) key gaps in knowledge of the underlying signaling pathways needed for activation;and (ii) lack of appropriate models to test outcomes in human cancers. We will determine the conditions necessary for this response and test the ability to treat human cancers with MIS. A second, non-overlapping approach will target the receptor directly as a 'bait'to deliver toxic agents to the cancer cells. Such specific delivery would increase treatment effect and decrease associated toxicities in normal tissues. This projects brings together two investigators with distinctly different areas of expertise to address both the fundamental biologic aspects of the pathway and the translational aspects of targeting this receptor in cancer.